Well, first of all, the question asks us to to list three different factors that could lead to this variation.
The first one is pressure, so, what happens is that, when the pressure changes with the height change, these plants develop in different ways. The second one is the oxygen, as we know, oxygen in higher elevations is less than in ocean elevation for example, so this can be a reason for this variation. The last one is the quantity of organic material on the soil, this can influence directly on the development of this population.
With that said, we need to write a hypothesis for one of these factors, let's choose the organic material because it's easier and cheaper to test. For that, the hypothesis is that, with less organic material available on the ground, the plant will grow smaller than on a normal soil. To test that, we need to grab samples of this flowering plant and put it at the same conditions as on the mountain, that is a possibility on a good lab, so after that, we'll change the quantity of organic material on some samples, to check if my hypothesis is right or not.
The positive results are that this is the reason why the plants grow smaller, so, with less organic material, the plants won't develop in the same way as it would happen with enough organic material. The negative results are that this is not the reason why these variations exist, so we need to test another factor to check why this variation is happening.
